1. Field of the invention
The present invention relates to optical shaped articles for CRT, and more specifically to optical shaped articles used for the CRT of projection TV, such as projection lens and filter.
2. Description of the prior art
An example of conventional rear-type projection TV is described by reference to FIG. 3. The projection TV 1 is so constructed that the image sent from a color CRT 2 is enlarged with a projection lens 3 to a prescribed size, which is then, via a reflecting mirror 4, projected on a screen 5. The color CRT 2 consists of three separate CRT's for red, green and blue, and forms an image.
The color signals sent from red and green CRT's among the above three CRT's however have spectral characteristics in the visible light region as shown in FIGS. 4 and 5, which contain noise wavelengths. Consequently, projection TV's employing NTSC, PAL or similar systems give red and green having a chromaticity far different from the primary color (primary R or primary G), i.e. the colors are far from natural red and green, whereby it is difficult to obtain high-quality color images.
Accordingly, an object of the present invention is to provide an optical shaped article for CRT that can solve the above problem by cutting noise wavelengths of color signals to expand color reproduction area, thus providing high-quality color images.
Another object of the present invention is to provide a projection TV housing CRT's provided with a projection lens or filter which is included in the above optical shaped articles.